Palming Pipe and Tuning Fork Lab

     In  both the Tuning Fork Lab and Palming Pipe Lab, we discovered standing waves, otherwise known as harmonics. First, we used a tuning fork and hit it against the rubber soles of our shoes. If you held the fork up to your ear you can hear the vibration which created sound (a musical note)!  Then, we used labquest  FFT to measure the peak of the sound. It looked like this:

       As you can see, some waves are more dominant than others, but they are all mathematically proportional. This means that these waves are standing waves or "stationary waves" that remain in a constant position. These are also known as harmonics. This graph means that we see multiple harmonics that are spaced evenly apart (they are multiples of the fundamental frequency, or the lowest frequency that makes a standing wave). After measuring the peak of the highest wave, we plugged that number into Wolfhram Alpha and converted from Hz to discover what musical not the fork made.

     Shown in the image above, musical instrument create music instead of noise because the instruments create a combination of waves with various frequencies that have whole number ratios. Noise on the other hand has frequencies that are NOT  mathematically proportional. 

The difference between a woodwind and a stringed instrument is that stringed instruments (guitar, violin, etc.)

 produce transverse waves, or waves in which the medium is perpendicular to the transfer of energy while woodwind instruments (flutes,clarinets,etc.) 

 produce longitudinal waves, or waves in which the medium moves parallel to the transport of energy.

In the Palm Pipe Lab, we used 

V = ( W ) x ( f ). Our whole group chose different pipes and used rulers to measure the legnth and width of the pipe. For my pipe, I measure .06m long and .015m wide. Then, we used the formula 

Length = 1/4 (W) - 1/4 (diameter)

After that, my measurements were a bit off but once we solved for the frequency we plugged it into 

V = ( W ) x ( f ). Since we already knew that sound travels at a constant of 343 m/s, it was easy finding the frequency of the wave. After finding the frequency, we once again went to Wolfram Alpha and converted Hz to discover a musical note that we used to play a song.

The Law of Refraction

This week, our job was to create an original image depicting what we have learned in class about Light Optics. Since I was interested in air to water refraction, I used a figurine to partially submerge in a glass of water. As you can see, the portion of the cat that is underwater looks larger than normal. It also seems displaced. How is this possible? Well, in this picture, light is moving from air to glass to water to glass and then back to air. Because air, glass, and water are different substances, the incident of refraction or the speed in which light moves through these different materials are different as well. For air, the incident of refraction (n) is 1 while n for glass is 1.52 and  n for water is 1.33 so when light passes from the air to glass to water it travels at different speeds. This is why the cat appears to look larger and displaced underwater. In order to determine how much the light refracted (the angle of refraction) we use the Snell's Law which states:

This image shows the angle of refraction from air to water

This is another image explaining refraction of light as it moves from air to water

                                              This image shows refraction of light to glass

Standard 6.3--Permanent and Temporary Magnets

Standard 6.3: Explain how objects like the earth and metals can be permanent or temporary magnets.

                                                                   MARS INTERIOR                                                           

                                                                  (solid)

One of the key concepts that we learned during this unit is that moving charges generate magnetic fields. We know that Earth generates a magnetic field because the outer core of Earth is molten, meaning that there are very hot metals such as iron and nickel moving around the outer core in liquid form . These metals have charges and these moving charges are what makes Earth one large magnet. In addition , Earth's rotation around the sun helps the current of the moving charges in the outer core to generate Earth's magnetic field that protects us from foreign space objects penetrating our atmosphere. Other planets aren't so lucky. Mars, for example, does not have a molten outer core and therefore no moving charges so it does not have a magnetic field. 


         EARTH INTERIOR

A magnetic domain is a region in which the magnetic fields of atoms are aligned (pointing in the same direction) and grouped together. Earth is a PERMANENT MAGNET, meaning that the domains are always aligned. As long as Earth has moving charges, it will always be magnetic. Paper clips are TEMPORARY MAGNETS,  meaning that they can be magnetic at times and not at others. When a paper clip comes in close contact with a permanent magnet, the domains of the paper clip line up and it becomes temporarily magnetic. When the paper clip is removed from the permanent magnet's magnetic field, the domains become askew and the paper clip is no longer magnetic. Items such as paper are never magnetic because their domains never align even when they come in contact with another magnet.

Lemon Lab

                           
This week, we started a new unit for electricity. In this lab, we expirimented with voltage ( a "field" surrounding a charged object). It's similar to the height needed for gravitational potential energy. The more height, the more Ug and the more voltage, the more Ue. We created a circuit, or a circular flow of electrons, using a lemon, copper penny, alligator chords, and a nail to create light. The more lemons that we had, the more voltage we measured. We related voltage to the batteries in our ipads. The article that I found discussed how massive the battery is in our iPads. Looking at the image above, it is clear that the battery takes up a massive portion of the device! According to my article, the ipad 3 has a 70% greater battery capacity than the previous generation-- It's larger in size than the 11-inch MacBook Air and nearly as big as the battery in today's 13-inch MacBook Air.

IPads specifically have lithium ion batteries.Lithium is well suited foe the iPads because of its ability to quickly recharge ,manageable size, and high power density. The voltage from the battery creates a large amount of electric potential energy that can be transferred into other types of energy such as sound, heat, and light.In our lab,  the energy created from the charged particles in the lemon was transferred into light. We talked in class about voltage as a mountain. In this case, the lemon was our mountain. Alone, the citrus in the lemon is neutral but when it comes in contact with charged particles such as copper and 
zinc, the lemon becomes charged and creates voltage.
                                                                                                                                     

Projectile Motion Reflection on Learning

This week's Big Questions:

What is a projectile? What is the general path of motion? Why?

In this lab we explored projectiles by shooting an "airball" with a basketball in the gym. Unfortunately, I was busy taking my driving test so I was not present for this part of the lab. Each person in our group video taped one another shooting the basketball with the app Video Physics. This app allowed us to track the ball's motion as it was shot using dots shown in the image below:

The dots showed us that the ball moves in an arc, which is the general path of motion. A projectile is any object projected into space with the use of a force but when the object is in motion, the only force acting on it is gravity. This can be anything from a cannon to a bullet shot from a gun to a volleyball being served over a net. Although there is air resistance in this experiment  it only really matters with sports such as baseball and golf. When we analyze the projectile of the basketball, we must first separate dimensions. In the x dimension (horizontally) , the ball is moving at constant speed because the ball has a constant slope which is shown below:

This is how a free body diagram looks with a projectile:

The ball never stops moving on the x-axis but on the y-axis, the ball decelerates, stops, and accelerates. This is where you can really see the arc shape of the ball. As it is moving upwards, the ball is losing speed because gravity is pulling the ball down. At the top, for one instant, the ball stops moving then proceeds downward. As it moves down, the ball begins to accelerate again and then hits the ground.How do we find the acceleration of the ball in the y-axis? Acceleration is the slope of velocity. So we use rise over run to find the slope. This was done by our ipads and is shown below:
        

We found the acceleration to be roughly -10N/kg 

Another expiriment that we performed in class tested Galileo's theory that all objects fall at the same rate, despite the amount of mass or matter. This is the only projectile that moves in a straight line, not an arc. We dropped a series of objects at the same time that have different masses. For example, we used a block of wood and a sticky note. The block of wood fell faster because the sticky note had more air resistance. When we crumpled the sticky note ( decreased the air resistance), the block of wood and the paper fell at the same rate. This also happened on the moon , where air resistance is not not a factor except the objects used were a hammer and a feather. Proving Galileo's theory right, they fell at the same rate.

Hover Disc--Centripetal Force

This Week's Big Questions:
1. What does it mean to analyze forces in 3D?
2. How do forces cause objects to move in a circle?
3. What does it mean to be in orbit? How do satellites orbit planets? How do planets orbit the sun?

 What does it mean to say that we live in a 3D universe? By using the term 3D, we are saying that there are 3 dimensions of space (x, y, and z). Examples of this on earth include the latitude, longitude and altitude of a particular spot on Earth. Actually, it may be better to say that we live in a 4D world. This includes time ( t ). The important thing to remember is that when we analyze these dimensions, we can analyze them separately or independent of one another using SIN and COS (or SOH CAH). Using these, we can analyze a piece of wire by making it a triangle (portrait problem). This week, we explored the use of forces involved in causing objects to move in a circle using a hover disk, which eliminated friction force (unlocked the ridges between the disk and the floor). We moved this disk in a circle using constant speed. When we drew the free body diagram of the disk as it was spinning, there were 3 forces acting on the disk (gravitational, normal, and tension) the normal and gravitational forces cancelled each other out because they were balanced--meaning that because the disk was travelling at constant speed (Newton's 1st law) the normal force was the same as the gravitational force. This left tension. This central pointing net force (centripetal) is what made the disk move in a circle. Without this net force, the disk proceeded in a straight line at constant speed. Since the disk felt a net force towards the center, it moved towards the center . But because it was moving fast enough, the disk began moving around the center. You can be at constant speed in a circle while accelerating. The only thing that changes is direction. Remember, acceleration does not necessarily mean speeding up. When an object is moving in a circle, it is accelerating because its direction of motion is changing and whenever the acceleration is perpendicular to the velocity, the object changes direction but is still at constant speed.

This relates to Earth and how we orbit around the sun. We are moving at constant speed (about 60,000 mph) around the sun with nothing to stop us. In this case, the centripetal force is the sun. Earth has a gravitational rope pulling us around the sun. This is what disproves the idea that there is no gravity in space. If there was no gravity (or no rope) the earth would move away from the sun in a straight line at constant speed. We got the initial speed that propelled us around the sun (just like the force that we applied to the disk in order to get it moving)  from the creation of our solar system. Even though the gravitational force is weaker, it still exists in space. In regards to the moon, the  center is Earth and the center pointing net force  (centripetal force) is gravity which it to fall around the earth. This is how orbits happen.